It is often desirable to drive vehicles over slippery, snow or ice covered roadways. Dual wheels require the installation of heavy chains when such conditions are encountered. A typical vehicle where such dual wheels are prevalently used might be in commercial or governmental vehicles such as large trucks or buses. However, such dual wheel configurations are increasingly utilized in private vehicles, such as large pickups or sport utility vehicles, and their use may be expected to expand even more widely in the future.
When "chain-up" conditions are encountered, the labor involved in the installation and removal of required chains is considerable. Many hours are consumed by drivers and support personnel to equip vehicles for operation in such adverse conditions. Moreover, the mere hassle of dealing with such equipment tempts some drivers to press on without installing chains, particularly in precautionary situations, and this often results in accidents with property damage and/or personal injury.
I am aware of various attempts in which an effort has been made to provide an improved, retractable studded tire, or to add a friction increasing device to a dual tire. In single width tires, such attempts are largely characterized by designs which include some sort of inflatable chamber which extends studs outward toward a road surface, from a stowed position where the studs have minimal or no contact with the road surface. Such extendible stud designs do not lend themselves to traction devices or treads other than studs.
In dual width wheels, complicated mechanical devices have been employed, or fixed inserts with inflatable studs have been employed. None of those designs have been wholly satisfactory, primarily because they require additional parts that are relatively foreign to the tire industry, and which parts are prone to breakage (under conditions in which they are not easily repaired).
One such prior art design is shown in Austrian Patentschrift Nr. 198148, issued Jun. 10, 1958. In one embodiment, his invention provides a radially extending tread portion which is mechanically affixed to a in inverted "T" post that is secured between the two wheels. However, his device does not provide for a simple, tread retraction when the extra traction is not necessary, rather, only the stud is pneumatically inflated and released.
Another design which superficially attempts to solve the same problem as the instant invention, at least to some remote extent, is disclosed in U.S. Pat. No. 2,201,632 issued May 21, 1940 to L. O. E. Roessel for ANTISKIDDING DEVICE FOR AUTOMOBILES. Roessel's design uses a mechanical geared device, with extendable radially extending spokes having at their distal end a claw foot device. These devices are placed between a pair of tires in a dual wheel assembly.
For the most part, the documents identified in the preceding paragraphs disclose devices which require the mechanical fasteners or mechanical adjustment to position the tread device. Roessel's device, having various adjustable parts, suffers from the shortcomings that they may become broken in use, thus resulting in the danger of reduced traction. And, although the Austrian patent shows a solid tread design with inflatable stud, the tread is basically fixed against the roadway whenever the device is employed, rather than being retractable, or cushioned against impact. Thus, the advantages of (a) my simple retainer ring design which may be used in wheels of conventional design with minimal modifications, (b) which enables dual tires to function normally when my retractable tread assembly is not installed, and (c) the avoidance of mechanical fasteners and mechanical gears, etc., as a means to engage the tread studs with the roadway, are important and self-evident.